package main

import (
      "fmt"
      "math/rand"
      "time"
      "sync"
      "runtime"
)

var wg sync.WaitGroup

func Sleep() {
    defer wg.Done()

    r := rand.Intn(3);
    if r == 0 {
      time.Sleep(10 * time.Millisecond) //0.01秒停止
    } else if r == 1 {
      time.Sleep(100 * time.Millisecond)  //0.1秒停止
    } else if r == 2 {
      time.Sleep(3000 * time.Millisecond) //3秒停止
    }
}

func main() {
  N := 8;
  runtime.GOMAXPROCS(N)

  idx := 0;
  for i:=0; i<18; i++ {
    fmt.Println("process:", i)
    wg.Add(1)
    idx += 1;
    go Sleep();
    if idx%N == 0 {
        wg.Wait();
    }
  }

  wg.Wait();
}